This invention relates to a suspension system that incorporates an automatic driver-controllable adjustment mechanism for setting the pitch of the axle. Pursuant to the invention, the pitch of the axle can be selectively set for self steering in either a forward or reverse direction.
In suspension systems for trailing axles and pusher axles, it is known that if the axle is installed with the proper pitch, the drag of the wheels will cause the axle to steer automatically in response to steering of the vehicle. It is also known in the art to provide a parallelogram arrangement of torque rods connected between a hanger and an axle seat to maintain a substantially constant pitch of the axle.
U.S. Pat. No. 4,132,432 to Raidel discloses an example of a suspension system wherein torque rods are connected between a hanger and an axle seat and are arranged in a parallelogram for maintaining a constant pitch of the axle. A lift spring is mounted between a plate on the hanger and a plate is connected to the lower torque rod. In the suspension system of this patent, as is typical, the axle pitch is constant and cannot be adjusted.
U.S. Pat. No. 4,132,432 also discloses an integral hanger and spring mount connected to an elongated longitudinal plate. The present suspension system is extremely compact and the hanger incorporates a cavity to accommodate the lift spring.